The present invention relates generally to crop harvesting machines and, more particularly, to shielding for a drive belt having toothed members projecting upwardly during a return run.
Generally, when a split sickle cutterbar, as is more particularly described in U.S. Pat. No. 3,577,716, is provided on a crop harvesting header, it is necessary to maintain proper timing between the opposing sickles. While a common V-belt drive mechanism is generally the least expensive, it does not provide the positive drive relationship necessary between the drive belt and the drive and driven sprockets to maintain the proper timing between opposing sickles.
A chain drive mechanism will provide the proper positive driving relationship between the chain and the drive and driven sprocket; however, a chain drive mechanism is noisy and has a relatively short life as compared to a belt drive. It has been found that a toothed drive belt which engages with a drive and driven sprocket having indentations corresponding to the drive belt teeth provides a proper combination of desirable characteristics and provides a positive drive relationship. However, the return run of such a toothed drive belt positions the teeth in an upwardly projecting position. Therefore, the return run of the drive belt is subject to having dirt and/or debris fill up the interstitial spaces between adjacent drive teeth such that the toothed belt in effect becomes a conveyor until the spaces between the teeth fill up and then operates as a smooth V-belt, thereby, disrupting the positive driving relationship between the toothed belt and the drive and driven sprockets.
Further complicating this problem is the movement of the driven sprocket in a generally vertical direction on flexible headers. If the driven sprocket moves with the corresponding movements of a floating cutterbar, the forward end of the drive belt necessarily moves therewith.